Ars Technica is running an interesting article about the Mail application on Windows 8. It's one of the first party Metro applications, and Ars' conclusion is that it's really, really not up to snuff - it can't even compare favourably to the mail application on Windows Phone. The sad thing is, however - this applies to virtually all Metro applications.

Why on earth do you reference "Carbon" here? Carbon was also deprecated when MacOS X was introduced in 2001. Developers were NEVER supposed to write Carbon applications when targeting MacOS X. Cocoa is and has always been the native API of MacOS X and it is STABLE.

The only API which is constantly broken is Win32 and other stuff from Microsoft. Ask any wine developer or developers at Steam.